Atherosclerosis is a progressive disease. In this disease, lesions of the arteries are formed by accumulation of plaque and neointimal hyperplasia causing an obstruction of blood flow. Often plaque is friable and may dislodge naturally or during an endovascular procedure, leading to embolization of a downstream vessel.
Endovascular clearing procedures to reduce or remove the obstructions to restore luminal diameter allows for increased blood flow to normal levels are well known. Removing the plaque has the effect of removing diseased tissue and helps to reverse the disease. Maintaining luminal diameter for a period of time (several to many weeks) allows remodeling of the vessel from the previous pathological state to a more normal state. Finally, it is the goal of an endovascular to prevent short term complications such as embolization or perforation of the vessel and long term complications such as ischemia from thrombosis or restenosis.
Various treatment modalities may help to accomplish treatment goals. In atherectomy, plaque is cut away, or excised. Various configurations are used including a rotating cylindrical shaver or a fluted cutter. The devices may include shielding by a housing for safety. The devices may also remove debris via trapping the debris in the catheter, in a downstream filter, or aspirating the debris. In some cases a burr may be used instead of a cutter, particularly to grind heavily calcified lesions into very small particle sizes. Aspiration may also be used with a burr-type atherectomy device.
Balloon angioplasty is another type of endovascular procedure. Balloon angioplasty expands and opens the artery by both displacing the plaque and compressing it. Balloon angioplasty is known to cause barotrauma to the vessel from the high pressures required to compress the plaque. This trauma leads to an unacceptably high rate of restenosis. Furthermore, this procedure may not be efficient for treatment of elastic-type plaque tissue, where such tissue can spring back to occlude the lumen.
When clearing such obstructions it is desirable to protect the vessel wall or wall of the body lumen being cleared and to debulk substantially all of a lesion. In additional cases, the procedure that clears obstructions may also be coupled with placement of an implant within the lumen. For example, it may be desirable to deploy a stent to maintain patency of a vessel for a period of time and/or to achieve local drug delivery by having the stent elute a drug or other bioactive substance.
On their own, stents fail to perform well in the peripheral vasculature for a variety of reasons. A stent with the necessary structural integrity to supply sufficient radial force to reopen the artery often does not perform well in the harsh mechanical environment of the peripheral vasculature. For example, the peripheral vasculature encounters a significant amount of compression, torsion, extension, and bending. Such an environment may lead to stent failure (strut cracking, stent crushing, etc.) that eventually compromises the ability of the stent to maintain lumen diameter over the long-term. On the other hand, a stent that is able to withstand the harsh mechanical aspects of the periphery often will not supply enough radial force to open the vessel satisfactorily. In many cases, medical practitioners desire the ability to combine endovascular clearing procedures with stenting. Such stenting may occur prior to, after, or both before and after the endovascular clearing procedure.
Accordingly, a need remains for devices that allow for improved atherectomy devices that are able to navigate through tortous anatomy and clear materials from body lumens (such as blood vessels) where the device includes features to allow for a safe, efficient and controlled fashion of shaving or grinding material within the body lumen while minimizing procedure times. In addition, there remains a need for devices that allow steering of the distal portion of the device while navigating through tortuous anatomy. The ability to steer assists the physician in accessing tortuous anatomy and can further assist in delivering a guidewire into the entrance of angled or tortuous vessel bifurcation/segments. This is possible because variations of the steerable atherectomy catheter described herein can also function as a ‘shuttle catheter’, where the physician can aim the distal tip into the vessel to be accessed and advancing the guidewire into that vessel from within the catheter.
There also remains a need for devices that are configured to steer but will remain in a straight configuration when not being articulated. It is generally known that conventional catheters that take a shape often bias to one side either through repeated articulation or even after being left in packing for any given period of time. Accordingly, when such steering features are combined with tissue debulking devices, there remains a risk of injury if the tissue debulking device has an undesirable bend when the device is supposed to be in a straight configuration.
The debulking devices described herein address the problems noted above as well as provide significant improved features to allow a physician to steer a debulking device through tortuous anatomy and remove tissue at a target site.